Systems for thermal-feedback-controlled rate of fluid flow to fluid-cooled antenna assembly and methods of directing energy to tissue using same

ABSTRACT

A method of directing energy to tissue using a fluid-cooled antenna assembly includes the initial step of providing an energy applicator. The energy applicator includes an antenna assembly and a hub providing at least one coolant connection to the energy applicator. The method also includes the steps of providing a coolant supply system including a fluid-flow path fluidly-coupled to the hub for providing fluid flow to the energy applicator, positioning the energy applicator in tissue for the delivery of energy to tissue when the antenna assembly is energized, and providing a thermal-feedback-controlled rate of fluid flow to the antenna assembly when energized using a feedback control system operably-coupled to a flow-control device disposed in fluid communication with the fluid-flow path.

BACKGROUND

1. Technical Field

The present disclosure relates to electrosurgical devices and, moreparticularly, to systems for thermal-feedback-controlled rate of fluidflow to a fluid-cooled antenna assembly and methods of directing energyto tissue using the same.

2. Discussion of Related Art

Treatment of certain diseases requires the destruction of malignanttissue growths, e.g., tumors. Electromagnetic radiation can be used toheat and destroy tumor cells. Treatment may involve inserting ablationprobes into tissues where cancerous tumors have been identified. Oncethe probes are positioned, electromagnetic energy is passed through theprobes into surrounding tissue.

In the treatment of diseases such as cancer, certain types of tumorcells have been found to denature at elevated temperatures that areslightly lower than temperatures normally injurious to healthy cells.Known treatment methods, such as hyperthermia therapy, heat diseasedcells to temperatures above 41° C. while maintaining adjacent healthycells below the temperature at which irreversible cell destructionoccurs. These methods involve applying electromagnetic radiation toheat, ablate and/or coagulate tissue. Microwave energy is sometimesutilized to perform these methods. Other procedures utilizingelectromagnetic radiation to heat tissue also include coagulation,cutting and/or ablation of tissue.

Electrosurgical devices utilizing electromagnetic radiation have beendeveloped for a variety of uses and applications. A number of devicesare available that can be used to provide high bursts of energy forshort periods of time to achieve cutting and coagulative effects onvarious tissues. There are a number of different types of apparatus thatcan be used to perform ablation procedures. Typically, microwaveapparatus for use in ablation procedures include a microwave generatorthat functions as an energy source, and a microwave surgical instrument(e.g., microwave ablation probe) having an antenna assembly fordirecting the energy to the target tissue. The microwave generator andsurgical instrument are typically operatively-coupled by a cableassembly having a plurality of conductors for transmitting microwaveenergy from the generator to the instrument, and for communicatingcontrol, feedback and identification signals between the instrument andthe generator.

There are several types of microwave probes in use, e.g., monopole,dipole and helical, which may be used in tissue ablation applications.In monopole and dipole antenna assemblies, microwave energy generallyradiates perpendicularly away from the axis of the conductor. Monopoleantenna assemblies typically include a single, elongated conductor. Atypical dipole antenna assembly includes two elongated conductors, whichare linearly aligned and positioned end-to-end relative to one anotherwith an electrical insulator placed therebetween. Helical antennaassemblies include a helically-shaped conductor that can be formed invarious configurations. The main modes of operation of a helical antennaassembly are normal mode (broadside), in which the field radiated by thehelix is maximum in a perpendicular plane to the helix axis, and axialmode (end fire), in which maximum radiation is along the helix axis.

A microwave transmission line typically includes a thin inner conductorthat extends along the longitudinal axis of the transmission line and issurrounded by a dielectric material and is further surrounded by anouter conductor around the dielectric material such that the outerconductor also extends along the transmission line axis. In onevariation of an antenna, a waveguiding structure, such as a length oftransmission line or coaxial cable, is provided with a plurality ofopenings through which energy “leaks” or radiates away from the guidingstructure. This type of construction is typically referred to as a“leaky coaxial” or “leaky wave” antenna.

Because of the small temperature difference between the temperaturerequired for denaturing malignant cells and the temperature normallyinjurious to healthy cells, a known heating pattern and precisetemperature control is needed to lead to more predictable temperaturedistribution to eradicate the tumor cells while minimizing the damage tosurrounding normal tissue. Excessive temperatures can cause adversetissue effects. During the course of heating, tissue in an overly-heatedarea may become desiccated and charred. As tissue temperature increasesto 100° C., tissue will lose water content due to evaporation or by thediffusion of liquid water from treated cells, and the tissue becomesdesiccated. This desiccation of the tissue changes the electrical andother material properties of the tissue, and may impede treatment. Forexample, as the tissue is desiccated, the electrical resistance of thetissue increases, making it increasingly more difficult to supply powerto the tissue. Desiccated tissue may also adhere to the device,hindering delivery of power. At tissue temperatures in excess of 100°C., the solid contents of the tissue begin to char. Like desiccatedtissue, charred tissue is relatively high in resistance to current andmay impede treatment.

Microwave ablation probes may utilize fluid circulation to coolthermally-active components and dielectrically load the antennaradiating section. During operation of a microwave ablation device, ifproper cooling is not maintained, e.g., flow of coolant fluid isinterrupted or otherwise insufficient to cool device componentssensitive to thermal failure, the ablation device may be susceptible torapid failures due to the heat generated from the increased reflectedpower. In such cases, the time to failure is dependent on the powerdelivered to the antenna assembly and the duration and degree to whichcoolant flow is reduced or interrupted.

Cooling the ablation probe may enhance the overall heating pattern ofthe antenna, prevent damage to the antenna and prevent harm to theclinician or patient. During some procedures, the amount of cooling maynot be sufficient to prevent excessive heating and resultant adversetissue effects. Some systems for cooling an ablation device may allowthe ablation device to be over-cooled, such as when the device isoperating at low power settings. Over-cooling may prevent propertreatment or otherwise impede device tissue effect by removing thermalenergy from the targeted ablation site.

SUMMARY

The present disclosure relates to an electrosurgical system including anelectrosurgical device adapted to direct energy to tissue, one or moretemperature sensors associated with the electrosurgical device, afluid-flow path leading to the electrosurgical device, and aflow-control device disposed in fluid communication with the fluid-flowpath. The system also includes a processor unit communicatively-coupledto the one or more temperature sensors and communicatively-coupled tothe flow-control device. The processor unit is configured to control theflow-control device based on determination of a desired fluid-flow rateusing one or more electrical signals outputted from the one or moretemperature sensors.

The present disclosure also relates to an electrosurgical systemincluding an electrosurgical device adapted to direct energy to tissueand a coolant supply system adapted to provide coolant fluid to theelectrosurgical device. The coolant supply system includes a coolantsource, a first fluid-flow path fluidly-coupled to the electrosurgicaldevice to provide fluid flow from the coolant source to theelectrosurgical device, a second fluid-flow path fluidly-coupled to theelectrosurgical device to provide fluid flow from the energy applicatorto the coolant source, a third fluid-flow path fluidly-coupled to thefirst fluid-flow path and the second fluid-flow path, and a flow-controldevice disposed in fluid communication with the third fluid-flow path.The system also includes one or more temperature sensors associated withthe electrosurgical device and a feedback control system adapted toprovide a thermal-feedback-controlled rate of fluid flow to theelectrosurgical device. The feedback control system includes a processorunit communicatively-coupled to the one or more temperature sensors andcommunicatively-coupled to the flow-control device. The processor unitis configured to control the flow-control device based on determinationof a desired fluid-flow rate using one or more electrical signalsoutputted from the one or more temperature sensors.

The present disclosure also relates to a method of directing energy totissue using a fluid-cooled antenna assembly including the initial stepof providing an energy applicator. The energy applicator includes anantenna assembly and a hub providing at least one coolant connection tothe energy applicator. The method also includes the steps of providing acoolant supply system including a fluid-flow path fluidly-coupled to thehub for providing fluid flow to the energy applicator, positioning theenergy applicator in tissue for the delivery of energy to tissue whenthe antenna assembly is energized, and providing athermal-feedback-controlled rate of fluid flow to the antenna assemblywhen energized using a feedback control system operably-coupled to aflow-control device disposed in fluid communication with the fluid-flowpath.

The present disclosure also relates to a method of directing energy totissue using a fluid-cooled antenna assembly including the initial stepsof providing an energy applicator and a coolant supply system adapted toprovide coolant fluid to the energy applicator. The energy applicatorincludes an antenna assembly and a coolant chamber adapted to circulatecoolant fluid around at least a portion of the antenna assembly. Thecoolant chamber is fluidly-coupled to the coolant supply system. Themethod also includes the steps of positioning the energy applicator intissue for the delivery of energy to tissue when the antenna assembly isenergized, and providing a thermal-feedback-controlled rate of fluidflow to the antenna assembly when energized by using a feedback controlsystem including a processor unit configured to control a flow-controldevice associated with the coolant supply system based on determinationof a desired fluid-flow rate using one or more electrical signalsoutputted from one or more temperature sensors associated with theenergy applicator.

BRIEF DESCRIPTION OF THE DRAWINGS

Objects and features of the presently-disclosed systems forthermal-feedback-controlled rate of fluid flow to a fluid-cooled antennaassembly and methods of directing energy to tissue using the same willbecome apparent to those of ordinary skill in the art when descriptionsof various embodiments thereof are read with reference to theaccompanying drawings, of which:

FIG. 1 is a schematic diagram of an electrosurgical system including anenergy-delivery device and a feedback control system operably associatedwith a fluid supply system fluidly-coupled to the energy-delivery devicein accordance with an embodiment of the present disclosure;

FIG. 2 is a schematic diagram of a feedback control system, such as thefeedback control system of FIG. 1, in accordance with an embodiment ofthe present disclosure;

FIG. 3 is a block diagram of an electrosurgical system including anembodiment of the electrosurgical power generating source of FIG. 1 inaccordance with the present disclosure;

FIG. 4 is a schematic diagram of an electrosurgical system including theenergy-delivery device of FIG. 1 shown with another embodiment of afeedback control system in operable connection with another embodimentof a fluid supply system in accordance with the present disclosure;

FIG. 5 is a schematic diagram of a feedback control system in accordancewith another embodiment of the present disclosure;

FIG. 6 is a flowchart illustrating a method of directing energy totissue using a fluid-cooled antenna assembly in accordance with anembodiment of the present disclosure; and

FIG. 7 is a flowchart illustrating a method of directing energy totissue using a fluid-cooled antenna assembly in accordance with anotherembodiment of the present disclosure.

DETAILED DESCRIPTION

Hereinafter, embodiments of the presently-disclosed systems forthermal-feedback-controlled rate of fluid flow to a fluid-cooled antennaassembly and methods of directing energy to tissue using the same aredescribed with reference to the accompanying drawings. Like referencenumerals may refer to similar or identical elements throughout thedescription of the figures. As shown in the drawings and as used in thisdescription, and as is traditional when referring to relativepositioning on an object, the term “proximal” refers to that portion ofthe apparatus, or component thereof, closer to the user and the term“distal” refers to that portion of the apparatus, or component thereof,farther from the user.

This description may use the phrases “in an embodiment,” “inembodiments,” “in some embodiments,” or “in other embodiments,” whichmay each refer to one or more of the same or different embodiments inaccordance with the present disclosure. For the purposes of thisdescription, a phrase in the form “A/B” means A or B. For the purposesof the description, a phrase in the form “A and/or B” means “(A), (B),or (A and B)”. For the purposes of this description, a phrase in theform “at least one of A, B, or C” means “(A), (B), (C), (A and B), (Aand C), (B and C), or (A, B and C)”.

Electromagnetic energy is generally classified by increasing energy ordecreasing wavelength into radio waves, microwaves, infrared, visiblelight, ultraviolet, X-rays and gamma-rays. As it is used in thisdescription, “microwave” generally refers to electromagnetic waves inthe frequency range of 300 megahertz (MHz) (3×10⁸ cycles/second) to 300gigahertz (GHz) (3×10¹¹ cycles/second).

As it is used in this description, “ablation procedure” generally refersto any ablation procedure, such as, for example, microwave ablation,radiofrequency (RF) ablation, or microwave or RF ablation-assistedresection. As it is used in this description, “energy applicator”generally refers to any device that can be used to transfer energy froma power generating source, such as a microwave or RF electrosurgicalgenerator, to tissue. For the purposes herein, the term “energy-deliverydevice” is interchangeable with the term “energy applicator”. As it isused in this description, “transmission line” generally refers to anytransmission medium that can be used for the propagation of signals fromone point to another.

As it is used in this description, “fluid” generally refers to a liquid,a gas, a liquid containing a dissolved gas or dissolved gases, a mixtureof gas and liquid, gas and suspended solids, liquid and suspendedsolids, or a mixture of gas, liquid and suspended solids. As it is usedin this description, “rate of fluid flow” generally refers to volumetricflow rate. Volumetric flow rate may be defined as a measure of thevolume of fluid passing a point in a system per unit time, e.g., cubicmeters per second (m³ s⁻¹) in SI units, or cubic feet per second (Cuft/s). Generally speaking, volumetric fluid-flow rate can be calculatedas the product of the cross-sectional area for flow and the flowvelocity. In the context of mechanical valves, the fluid-flow rate, inthe given through-flow direction, may be considered to be a function ofthe variable restriction geometry for a given flow passage configurationand pressure drop across the restriction. For the purposes herein, theterm “fluid-flow rate” is interchangeable with the term “rate of fluidflow”.

As it is used in this description, “pressure sensor” generally refers toany pressure-sensing device capable of generating a signalrepresentative of a pressure value. For the purposes herein, the term“pressure transducer” is interchangeable with the term “pressuresensor”.

As it is used herein, the term “computer” generally refers to anythingthat transforms information in a purposeful way. For the purposes ofthis description, the terms “software” and “code” should be interpretedas being applicable to software, firmware, or a combination of softwareand firmware. For the purposes of this description, “non-transitory”computer-readable media include all computer-readable media, with thesole exception being a transitory, propagating signal.

Various embodiments of the present disclosure provide systems forthermal-feedback-controlled rate of fluid flow to an electrosurgicaldevice, such as an ablation probe including a fluid-cooled antennaassembly. Embodiments may be implemented using electromagnetic radiationat microwave frequencies or at other frequencies. An electrosurgicalsystem including a coolant supply system and a feedback control systemadapted to provide a thermal-feedback-controlled rate of fluid flow toan energy applicator, according to various embodiments, is designed andconfigured to operate between about 300 MHz and about 10 GHz. Systemsfor thermal-feedback-controlled rate of fluid flow to electrosurgicaldevices, as described herein, may be used in conjunction with varioustypes of devices, such as microwave antenna assemblies having either astraight or looped radiating antenna portion, etc., which may beinserted into or placed adjacent to tissue to be treated.

Various embodiments of the presently-disclosed electrosurgical systemsincluding a feedback control system adapted to provide athermal-feedback-controlled rate of fluid flow to an energy applicatordisposed in fluid communication with a coolant supply system aresuitable for microwave ablation and for use to pre-coagulate tissue formicrowave ablation-assisted surgical resection. Although various methodsdescribed hereinbelow are targeted toward microwave ablation and thecomplete destruction of target tissue, it is to be understood thatmethods for directing electromagnetic radiation may be used with othertherapies in which the target tissue is partially destroyed or damaged,such as, for example, to prevent the conduction of electrical impulseswithin heart tissue. In addition, although the following descriptiondescribes the use of a dipole microwave antenna, the teachings of thepresent disclosure may also apply to a monopole, helical, or othersuitable type of antenna assembly.

FIG. 1 shows an electrosurgical system 10 according to an embodiment ofthe present disclosure that includes an energy applicator or probe 100,an electrosurgical power generating source 28, e.g., a microwave or RFelectrosurgical generator, and a feedback control system 14 operablyassociated with a coolant supply system 11. Probe 100 isoperably-coupled to the electrosurgical power generating source 28, anddisposed in fluid communication with the coolant supply system 11. Insome embodiments, one or more components of the coolant supply system 11may be integrated fully or partially into the electrosurgical powergenerating source 28. Coolant supply system 11, which is described inmore detail later in this description, is adapted to provide coolantfluid “F” to the probe 100. Probe 100, which is described in more detaillater in this description, may be integrally associated with a hub 142configured to provide electrical and/or coolant connections to theprobe. In some embodiments, the probe 100 may extend from a handleassembly (not shown).

In some embodiments, the electrosurgical system 10 includes one or moresensors capable of generating a signal indicative of a temperature of amedium in contact therewith (referred to herein as temperature sensors)and/or one or more sensors capable of generating a signal indicative ofa rate of fluid flow (referred to herein as flow sensors). In suchembodiments, the feedback control system 14 may be adapted to provide athermal-feedback-controlled rate of fluid flow to the probe 100 usingone or more signals output from one or more temperature sensors and/orone or more flow sensors operably associated with the probe 100 and/orconduit fluidly-coupled to the probe 100.

An embodiment of a feedback control system, such as the feedback controlsystem 14 of FIG. 1, in accordance with the present disclosure, is shownin more detail in FIG. 2. It is to be understood, however, that otherfeedback control system embodiments (e.g., feedback control systems 414and 514 shown in FIGS. 4 and 5, respectively) may be used in conjunctionwith coolant supply systems in various configurations. In someembodiments, the feedback control system 14, or component(s) thereof,may be integrated fully or partially into the electrosurgical powergenerating source 28.

In the embodiment shown in FIG. 1, the feedback control system 14 isoperably associated with a processor unit 82 disposed within orotherwise associated with the electrosurgical power generating source28. Processor unit 82 may be communicatively-coupled to one or morecomponents or modules of the electrosurgical power generating source 28,e.g., a user interface 121 and a generator module 86. Processor unit 82may additionally, or alternatively, be communicatively-coupled to one ormore temperature sensors (e.g., two sensors “TS₁” and “TS₂” shown inFIG. 1) and/or one or more flow sensors (e.g., one sensor “FS₁” shown inFIG. 1) for receiving one or more signals indicative of a temperature(referred to herein as temperature data) and/or one or more signalsindicative of a flow rate (referred to herein as flow data).Transmission lines may be provided to electrically couple thetemperature sensors, flow sensors and/or other sensors, e.g., pressuresensors, to the processor unit 82.

Feedback control system embodiments may additionally, or alternatively,be operably associated with a processor unit deployed in a standaloneconfiguration, and/or a processor unit disposed within the probe 100 orotherwise associated therewith. In some embodiments, where the probe 100extends from a handle assembly (not shown), the feedback control systemmay be operably associated with a processor unit disposed within thehandle assembly. Examples of handle assembly embodiments are disclosedin commonly assigned U.S. patent application Ser. No. 12/686,726 filedon Jan. 13, 2010, entitled “ABLATION DEVICE WITH USER INTERFACE ATDEVICE HANDLE, SYSTEM INCLUDING SAME, AND METHOD OF ABLATING TISSUEUSING SAME”.

Electrosurgical power generating source 28 may include any generatorsuitable for use with electrosurgical devices, and may be configured toprovide various frequencies of electromagnetic energy. In someembodiments, the electrosurgical power generating source 28 isconfigured to provide microwave energy at an operational frequency fromabout 300 MHz to about 10 GHz. In some embodiments, the electrosurgicalpower generating source 28 is configured to provide electrosurgicalenergy at an operational frequency from about 400 KHz to about 500 KHz.An embodiment of an electrosurgical power generating source, such as theelectrosurgical power generating source 28 of FIG. 1, in accordance withthe present disclosure, is shown in more detail in FIG. 3.

Probe 100 may include one or more antennas of any suitable type, such asan antenna assembly (or antenna array) suitable for use in tissueablation applications. For ease of explanation and understanding, theprobe 100 is described as including a single antenna assembly 112. Insome embodiments, the antenna assembly 112 is substantially disposedwithin a sheath 138. Probe 100 generally includes a coolant chamber 137defined about the antenna assembly 112. In some embodiments, the coolantchamber 137, which is described in more detail later in thisdescription, includes an interior lumen defined by the sheath 138.

Probe 100 may include a feedline 110 coupled to the antenna assembly112. A transmission line 16 may be provided to electrically couple thefeedline 110 to the electrosurgical power generating source 28. Feedline110 may be coupled to a connection hub 142, which is described in moredetail later in this description, to facilitate the flow of coolantand/or buffering fluid into, and out of, the probe 100.

In the embodiment shown in FIG. 1, the feedback control system 14 isoperably associated with a flow-control device 50 disposed in fluidcommunication with a fluid-flow path of the coolant supply system 11(e.g., first coolant path 19) fluidly-coupled to the probe 100.Flow-control device 50 may include any suitable device capable ofregulating or controlling the rate of fluid flow passing though theflow-control device 50, e.g., a valve of any suitable type operable toselectively impede or restrict flow of fluid through passages in thevalve. Processor unit 82 may be configured to control the flow-controldevice 50 based on determination of a desired fluid-flow rate usingtemperature data received from one or more temperature sensors (e.g.,“TS₁”, “TS₂” through “TS_(N)” shown in FIG. 2).

In some embodiments, the flow-control device 50 includes a valve 52including a valve body 54 and an electromechanical actuator 56operatively-coupled to the valve body 54. Valve body 54 may beimplemented as a ball valve, gate valve, butterfly valve, plug valve, orany other suitable type of valve. In the embodiment shown in FIG. 1, theactuator 56 is communicatively-coupled to the processor unit 82 via atransmission line 32. Processor unit 82 may be configured to control theflow-control device 50 by activating the actuator 56 to selectivelyadjust the fluid-flow rate in a fluid-flow path (e.g., first coolantpath 19 of the coolant supply system 11) fluidly-coupled to theconnection hub 142 to achieve a desired fluid-flow rate. The desiredfluid-flow rate may be determined by a computer program and/or logiccircuitry associated with the processor unit 82. The desired fluid-flowrate may additionally, or alternatively, be selected from a look-uptable “T_(X,Y)” (shown in FIGS. 2 and 5) or determined by a computeralgorithm stored within a memory device 8 (shown in FIGS. 2 and 5).

Embodiments including a suitable pressure-relief device 40 disposed influid communication with the diversion flow path 21 may allow thefluid-movement device 60 to run at a substantially constant speed and/orunder a near-constant load (head pressure) regardless of the selectiveadjustment of the fluid-flow rate in the first coolant path 19.Utilizing a suitable pressure-relief device 40 disposed in fluidcommunication with the diversion flow path 21, in accordance with thepresent disclosure, may allow the fluid-movement device 60 to beimplemented as a single speed device, e.g., a single speed pump.

Feedback control system 14 may utilize data “D” (e.g., datarepresentative of a mapping of temperature data to settings for properlyadjusting one or more operational parameters of the flow-control device50 to achieve a desired temperature and/or a desired ablation) stored ina look-up table “T_(X,Y)” (shown in FIGS. 2 and 5), where X denotescolumns and Y denotes rows, or other data structure, to determine thedesired fluid-flow rate. In the embodiment shown in FIG. 1, theelectrosurgical system 10 includes a first temperature sensor “TS₁”capable of generating a signal indicative of a temperature of a mediumin contact therewith and a second temperature sensor “TS₂” capable ofgenerating a signal indicative of a temperature of a medium in contacttherewith. Feedback control system 14 may be configured to utilizesignals received from the first temperature sensor “TS₁” and/or thesecond temperature sensor “TS₂” to control the flow-control device 50.

In some embodiments, the electrosurgical system 10 includes a flowsensor “FS₁” communicatively-coupled to the processor unit 82, e.g., viaa transmission line 36. In some embodiments, the flow sensor “FS₁” maybe disposed in fluid communication with the first coolant path 19 or thesecond coolant path 20. Processor unit 82 may be configured to controlthe flow-control device 50 based on determination of a desiredfluid-flow rate using one or more signals received from the flow sensor“FS₁”. In some embodiments, the processor unit 82 may be configured tocontrol the flow-control device 50 based on determination of a desiredfluid-flow rate using one or more signals received from the flow sensor“FS₁” in conjunction with one or more signals received from the firsttemperature sensor “TS₁” and/or the second temperature sensor “TS₂”.Although the electrosurgical system 10 shown in FIG. 1 includes one flowsensor “FS₁”, alternative embodiments may be implemented with aplurality of flow sensors (e.g., “FS₁”, “FS₂” through “FS_(M)” shown inFIG. 2) adapted to provide a measurement of the rate of fluid flow intoand/or out of the probe 100 and/or conduit fluidly-coupled to the probe100.

Electrosurgical system 10 may additionally, or alternatively, includeone or more pressure sensors (e.g., “PS₁”, “PS₂” through “PS_(K)” shownin FIG. 5) adapted to provide a measurement of the fluid pressure in theprobe 100 and/or conduit fluidly-coupled to the probe 100. In someembodiments, the electrosurgical system 10 includes one or more pressuresensors (e.g., pressure sensor 70) disposed in fluid communication withone or more fluid-flow paths (e.g., first coolant path 19) of thecoolant supply system 11 as opposed to a pressure sensor disposed withinthe probe 100, reducing cost and complexity of the probe 100.

In the embodiment shown in FIG. 1, the processor unit 82 is operablyassociated with a pressure sensor 70 disposed in fluid communicationwith a fluid-flow path of the coolant supply system 11. Processor unit82 may be communicatively-coupled to the pressure sensor 70 via atransmission line 30 or wireless link. Processor unit 82 mayadditionally, or alternatively, be operably associated with one or morepressure sensors disposed within the probe 100, e.g., disposed in fluidcommunication with the coolant chamber 137.

Pressure sensor 70 may include any suitable type of pressure sensor,pressure transducer, pressure transmitter, or pressure switch. Pressuresensor 70 (also referred to herein as “pressure transducer”) may includea variety of components, e.g., resistive elements, capacitive elementsand/or piezo-resistive elements, and may be disposed at any suitableposition in the coolant supply system 11. In some embodiments, thepressure transducer 70 is disposed in fluid communication with the firstcoolant path 19 located between the fluid-movement device 60 and theflow-control device 50, e.g., placed at or near the flow-control device50.

In some embodiments, the processor unit 82 may be configured to controlthe flow-control device 50 based on determination of a desiredfluid-flow rate using pressure data received from one or more pressuresensors. In some embodiments, the processor unit 82 may be configured tocontrol the flow-control device 50 based on determination of a desiredfluid-flow rate using one or more signals received from the firsttemperature sensor “TS₁” and/or the second temperature sensor “TS₂”and/or the flow sensor “FS₁” in conjunction with one or more signalsreceived from the pressure transducer 70.

In some embodiments, the processor unit 82 may be configured to controlthe amount of power delivered to the antenna assembly 112 based on timeand power settings provided by the user in conjunction with sensedtemperature signals indicative of a temperature of a medium, e.g.,coolant fluid “F”, in contact with one or one temperature sensorsoperably associated with the antenna assembly 112 and/or the connectionhub 142. In some embodiments, the processor unit 82 may be configured todecrease the amount of power delivered to the antenna assembly 112 whensensed temperature signals indicative of a temperature below apredetermined temperature threshold are received by processor unit 82,e.g., over a predetermined time interval.

Processor unit 82 may be configured to control one or more operatingparameters associated with the electrosurgical power generating source28 based on determination of whether the pressure level of fluid in theprobe 100 and/or conduit fluidly-coupled to the probe 100 is above apredetermined threshold using pressure data received from one or morepressure sensors, e.g., pressure transducer 70. Examples of operatingparameters associated with the electrosurgical power generating source28 include without limitation temperature, impedance, power, current,voltage, mode of operation, and duration of application ofelectromagnetic energy.

In some embodiments, the output signal of the pressure transducer 70,representing a pressure value and possibly amplified and/or conditionedby means of suitable components (not shown), is received by theprocessor unit 82 and used for determination of whether the pressurelevel of fluid in the probe 100 and/or conduit fluidly-coupled to theprobe 100 is above a predetermined threshold in order to control whenpower is delivered to the antenna assembly 112. In some embodiments, inresponse to a determination that the pressure level of fluid in theprobe 100 and/or conduit fluidly-coupled to the probe 100 is below thepredetermined threshold, the processor unit 82 may be configured todecrease the amount of power delivered to the antenna assembly 112and/or to stop energy delivery between the electrosurgical powergenerating source 28 and the probe 100. In some embodiments, theprocessor unit 82 may be configured to enable energy delivery betweenthe electrosurgical power generating source 28 and the probe 100 basedon determination that the pressure level of fluid in the probe 100and/or conduit fluidly-coupled to the probe 100 is above thepredetermined threshold.

In some embodiments, the pressure transducer 70 is adapted to output apredetermined signal to indicate a sensed pressure below that of theburst pressure of the pressure-relief device 40. A computer programand/or logic circuitry associated with the processor unit 82 may beconfigured to enable the electrosurgical power generating source 28 andthe flow-control device 50 in response to a signal from the pressuretransducer 70. A computer program and/or logic circuitry associated withthe processor unit 82 may be configured to output a signal indicative ofan error code and/or to activate an indicator unit 129 if a certainamount of time elapses between the point at which energy delivery to theprobe 100 is enabled and when the pressure signal is detected, e.g., toensure that the fluid-movement device 60 is turned on and/or that theprobe 100 is receiving flow of fluid before the antenna assembly 112 canbe activated.

As shown in FIG. 1, a feedline 110 couples the antenna assembly 112 to aconnection hub 142. Connection hub 142 may have a variety of suitableshapes, e.g., cylindrical, rectangular, etc. Connection hub 142generally includes a hub body 145 defining an outlet fluid port 177 andan inlet fluid port 179. Hub body 145 may include one or more branches,e.g., three branches 164, 178 and 176, extending from one or moreportions of the hub body 145. In some embodiments, one or more branchesextending from the hub body 145 may be configured to house one or moreconnectors and/or ports, e.g., to facilitate the flow of coolant and/orbuffering fluid into, and out of, the connection hub 142.

In the embodiment shown in FIG. 1, the hub body 145 includes a firstbranch 164 adapted to house a cable connector 165, a second branch 178adapted to house the inlet fluid port 179, and a third branch 176adapted to house the outlet fluid port 177. It is to be understood,however, that other connection hub embodiments may also be used.Examples of hub embodiments are disclosed in commonly assigned U.S.patent application Ser. No. 12/401,268 filed on Mar. 10, 2009, entitled“COOLED DIELECTRICALLY BUFFERED MICROWAVE DIPOLE ANTENNA”, and U.S. Pat.No. 7,311,703, entitled “DEVICES AND METHODS FOR COOLING MICROWAVEANTENNAS”.

In some embodiments, the flow sensor “FS₁” is disposed in fluidcommunication with the first coolant path 19, e.g., disposed within theinlet fluid port 179 or otherwise associated with the second branch 178,and the second temperature sensor “TS₂” is disposed in fluidcommunication with the second coolant path 20, e.g., disposed within theoutlet fluid port 177 or otherwise associated with the third branch 176.In other embodiments, the second temperature sensor “TS₂” may bedisposed within the inlet fluid port 179 or otherwise associated withthe second branch 178, and the flow sensor “FS₁” may be disposed withinthe outlet fluid port 177 or otherwise associated with the third branch176.

Coolant supply system 11 generally includes a substantially closed loophaving a first coolant path 19 leading to the probe 100 and a secondcoolant path 20 leading from the probe 100, a coolant source 90, and afluid-movement device 60, e.g., disposed in fluid communication with thefirst coolant path 19. In some embodiments, the coolant supply system 11includes a third coolant path 21 (also referred to herein as a“diversion flow path”) disposed in fluid communication with the firstcoolant path 19 and the second coolant path 20. The conduit layouts ofthe first coolant path 19, second coolant path 20 and third coolant path21 may be varied from the configuration depicted in FIG. 1.

In some embodiments, a pressure-relief device 40 may be disposed influid communication with the diversion flow path 21. Pressure-reliefdevice 40 may include any type of device, e.g., a spring-loadedpressure-relief valve, adapted to open at a predetermined set pressureand to flow a rated capacity at a specified over-pressure. In someembodiments, one or more flow-restrictor devices (not shown) suitablefor preventing backflow of fluid into the first coolant path 19 may bedisposed in fluid communication with the diversion flow path 21.Flow-restrictor devices may include a check valve or any other suitabletype of unidirectional flow restrictor or backflow preventer, and may bedisposed at any suitable position in the diversion flow path 21 toprevent backflow of fluid from the diversion flow path 21 into the firstcoolant path 19.

In some embodiments, the first coolant path 19 includes a first coolantsupply line 66 leading from the coolant source 90 to the fluid-movementdevice 60, a second coolant supply line 67 leading from thefluid-movement device 60 to the flow-control device 50, and a thirdcoolant supply line 68 leading from the flow-control device 50 to theinlet fluid port 179 defined in the second branch 178 of the connectionhub body 145, and the second coolant path 20 includes a first coolantreturn line 95 leading from the outlet fluid port 177 defined in thethird branch 176 of the hub body 145 to the coolant source 90.Embodiments including the diversion flow path 21 may include a secondcoolant return line 94 fluidly-coupled to the second coolant supply line67 and the first coolant return line 95. Pressure-relief device 40 maybe disposed at any suitable position in the second coolant return line94. The spacing and relative dimensions of coolant supply lines andcoolant return lines may be varied from the configuration depicted inFIG. 1.

Coolant source 90 may be any suitable housing containing a reservoir ofcoolant fluid “F”. Coolant fluid “F” may be any suitable fluid that canbe used for cooling or buffering the probe 100, e.g., deionized water,or other suitable cooling medium. Coolant fluid “F” may have dielectricproperties and may provide dielectric impedance buffering for theantenna assembly 112. Coolant fluid “F” may be a conductive fluid, suchas a saline solution, which may be delivered to the target tissue, e.g.,to decrease impedance and allow increased power to be delivered to thetarget tissue. A coolant fluid “F” composition may vary depending upondesired cooling rates and the desired tissue impedance matchingproperties. Various fluids may be used, e.g., liquids including, but notlimited to, water, saline, perfluorocarbon, such as the commerciallyavailable Fluorinert® perfluorocarbon liquid offered by Minnesota Miningand Manufacturing Company (3M), liquid chlorodifluoromethane, etc. Inother variations, gases (such as nitrous oxide, nitrogen, carbondioxide, etc.) may also be utilized as the cooling fluid. In yet anothervariation, a combination of liquids and/or gases, including, forexample, those mentioned above, may be utilized as the coolant fluid“F”.

In the embodiment shown in FIG. 1, the fluid-movement device 60 isprovided in the first coolant path 19 to move the coolant fluid “F”through the first coolant path 19 and into, and out of, the probe 100.Fluid-movement device 60 may include valves, pumps, power units,actuators, fittings, manifolds, etc. The position of the fluid-movementdevice 60, e.g., in relation to the coolant source 90, may be variedfrom the configuration depicted in FIG. 1. Although the coolant supplysystem 11 shown in FIG. 1 includes a single, fluid-movement device 60located in the first coolant path 19, various combinations of differentnumbers of fluid-movement devices, variedly-sized and variedly-spacedapart from each other, may be provided in the first coolant path 19and/or the second coolant path 20.

In some embodiments, the probe 100 includes a feedline 110 that couplesthe antenna assembly 112 to a hub, e.g., connection hub 142, thatprovides electrical and/or coolant connections to the probe 100.Feedline 110 may be formed from a suitable flexible, semi-rigid or rigidmicrowave conductive cable. Feedline 110 may be constructed of a varietyof electrically-conductive materials, e.g., copper, gold, or otherconductive metals with similar conductivity values. Feedline 110 may bemade of stainless steel, which generally offers the strength required topuncture tissue and/or skin.

In some variations, the antenna assembly 112 includes a distal radiatingportion 105 and a proximal radiating portion 140. In some embodiments, ajunction member (not shown), which is generally made of a dielectricmaterial, couples the proximal radiating section 140 and the distalradiating section 105. In some embodiments, the distal and proximalradiating sections 105, 140 align at the junction member and are alsosupported by an inner conductor (not shown) that extends at leastpartially through the distal radiating section 105.

Antenna assembly 112 may be provided with an end cap or tapered portion120, which may terminate in a sharp tip 123 to allow for insertion intotissue with minimal resistance. One example of a straight probe with asharp tip that may be suitable for use as the energy applicator 100 isan EVIDENT™ microwave ablation probe offered by Covidien. The end cap ortapered portion 120 may include other shapes, such as, for example, atip 123 that is rounded, flat, square, hexagonal, or cylindroconical.End cap or tapered portion 120 may be formed of a material having a highdielectric constant, and may be a trocar.

Sheath 138 generally includes an outer jacket 139 defining a lumen intowhich the antenna assembly 112, or portion thereof, may be positioned.In some embodiments, the sheath 138 is disposed over and encloses thefeedline 110, the proximal radiating portion 140 and the distalradiating portion 105, and may at least partially enclose the end cap ortapered portion 120. The outer jacket 139 may be formed of any suitablematerial, such as, for example, polymeric or ceramic materials. Theouter jacket 139 may be a water-cooled catheter formed of a materialhaving low electrical conductivity.

In accordance with the embodiment shown in FIG. 1, a coolant chamber 137is defined by the outer jacket 139 and the end cap or tapered portion120. Coolant chamber 137 is disposed in fluid communication with theinlet fluid port 179 and the outlet fluid port 177 and adapted tocirculate coolant fluid “F” therethrough, and may include baffles,multiple lumens, flow restricting devices, or other structures that mayredirect, concentrate, or disperse flow depending on their shape.Examples of coolant chamber embodiments are disclosed in commonlyassigned U.S. patent application Ser. No. 12/350,292 filed on Jan. 8,2009, entitled “CHOKED DIELECTRIC LOADED TIP DIPOLE MICROWAVE ANTENNA”,commonly assigned U.S. patent application Ser. No. 12/401,268 filed onMar. 10, 2009, entitled “COOLED DIELECTRICALLY BUFFERED MICROWAVE DIPOLEANTENNA”, and U.S. Pat. No. 7,311,703, entitled “DEVICES AND METHODS FORCOOLING MICROWAVE ANTENNAS”. The size and shape of the sheath 138 andthe coolant chamber 137 extending therethrough may be varied from theconfiguration depicted in FIG. 1.

During microwave ablation, e.g., using the electrosurgical system 10,the probe 100 is inserted into or placed adjacent to tissue andmicrowave energy is supplied thereto. Ultrasound or computed tomography(CT) guidance may be used to accurately guide the probe 100 into thearea of tissue to be treated. Probe 100 may be placed percutaneously oratop tissue, e.g., using conventional surgical techniques by surgicalstaff. A clinician may pre-determine the length of time that microwaveenergy is to be applied. Application duration may depend on many factorssuch as tumor size and location and whether the tumor was a secondary orprimary cancer. The duration of microwave energy application using theprobe 100 may depend on the progress of the heat distribution within thetissue area that is to be destroyed and/or the surrounding tissue.Single or multiple probes 100 may be used to provide ablations in shortprocedure times, e.g., a few seconds to minutes, to destroy cancerouscells in the target tissue region.

A plurality of probes 100 may be placed in variously arrangedconfigurations to substantially simultaneously ablate a target tissueregion, making faster procedures possible. Multiple probes 100 can beused to synergistically create a large ablation or to ablate separatesites simultaneously. Tissue ablation size and geometry is influenced bya variety of factors, such as the energy applicator design, number ofenergy applicators used simultaneously, time and wattage.

In operation, microwave energy having a wavelength, lambda (λ), istransmitted through the antenna assembly 112, e.g., along the proximaland distal radiating portions 140, 105, and radiated into thesurrounding medium, e.g., tissue. The length of the antenna forefficient radiation may be dependent on the effective wavelength λ_(eff)which is dependent upon the dielectric properties of the medium beingradiated. Antenna assembly 112, through which microwave energy istransmitted at a wavelength λ, may have differing effective wavelengthsλ_(eff) depending upon the surrounding medium, e.g., liver tissue asopposed to breast tissue.

In some embodiments, the electrosurgical system 10 includes a firsttemperature sensor “TS₁” disposed within a distal radiating portion 105of the antenna assembly 112. First temperature sensor “TS₁” may bedisposed within or contacting the end cap or tapered portion 120. It isto be understood that the first temperature sensor “TS₁” may be disposedat any suitable position to allow for the sensing of temperature.Processor unit 82 may be electrically connected by a transmission line34 to the first temperature sensor “TS₁”. Sensed temperature signalsindicative of a temperature of a medium in contact with the firsttemperature sensor “TS₁” may be utilized by the processor unit 82 tocontrol the flow of electrosurgical energy and/or the flow rate ofcoolant to attain the desired ablation.

Electrosurgical system 10 may additionally, or alternatively, include asecond temperature sensor “TS₂” disposed within the outlet fluid port177 or otherwise associated with the third branch 176 of the hub body145. Processor unit 82 may be electrically connected by a transmissionline 38 to the second temperature sensor “TS₂”. First temperature sensor“TS₁” and/or the second temperature sensor “TS₂” may be a thermocouple,thermistor, or other temperature sensing device. A plurality of sensorsmay be utilized including units extending outside the tip 123 to measuretemperatures at various locations in the proximity of the tip 123.

FIG. 2 schematically illustrates an embodiment of a feedback controlsystem, such as the feedback control system 14 of FIG. 1, in accordancewith the present disclosure, that includes the processor unit 82 and amemory device 8 in operable connection with the processor unit 82. Insome embodiments, the memory device 8 may be associated with theelectrosurgical power generating source 28. In some embodiments, thememory device 8 may be implemented as a storage device 88 (shown in FIG.3) integrated into the electrosurgical power generating source 28. Insome embodiments, the memory device 8 may be implemented as an externaldevice 81 (shown in FIG. 3) communicatively-coupled to theelectrosurgical power generating source 28.

In some embodiments, the processor unit 82 is communicatively-coupled tothe flow-control device 50, e.g., via a transmission line “L₅”, and maybe communicatively-coupled to the fluid-movement device 60, e.g., via atransmission line “L₆”. In some embodiments, the processor unit 82 maybe configured to control one or more operational parameters of thefluid-movement device 60 to selectively adjust the fluid-flow rate in afluid-flow path (e.g., first coolant path 19) of the coolant supplysystem 11. In one non-limiting example, the fluid-movement device 60 isimplemented as a multi-speed pump, and the processor unit 82 may beconfigured to vary the pump speed to selectively adjust the fluid-flowrate to attain a desired fluid-flow rate.

Processor unit 82 may be configured to execute a series of instructionsto control one or more operational parameters of the flow-control device50 based on determination of a desired fluid-flow rate using temperaturedata received from one or more temperature sensors, e.g., “TS₁”, “TS₂”through “TS_(N)”, where N is an integer. The temperature data may betransmitted via transmission lines “L₁”, “L₂” through “L_(N)” orwirelessly transmitted. One or more flow sensors, e.g., “FS₁”, “FS₂”through “FS_(M)”, where M is an integer, may additionally, oralternatively, be communicatively-coupled to the processor unit 82,e.g., via transmission lines “L₃”, “L₄” through “L_(M)”. In someembodiments, signals indicative of the rate of fluid flow into and/orout of the probe 100 and/or conduit fluidly-coupled to the probe 100received from one or more flow sensors “FS₁”, “FS₂” through “FS_(M)” maybe used by the processor unit 82 to determine a desired fluid-flow rate.In such embodiments, flow data may be used by the processor unit 82 inconjunction with temperature data, or independently of temperature data,to determine a desired fluid-flow rate. The desired fluid-flow rate maybe selected from a look-up table “T_(X,Y)” or determined by a computeralgorithm stored within the memory device 8.

In some embodiments, an analog signal that is proportional to thetemperature detected by a temperature sensor, e.g., a thermocouple, maybe taken as a voltage input that can be compared to a look-up table“T_(X,Y)” for temperature and fluid-flow rate, and a computer programand/or logic circuitry associated with the processor unit 82 may be usedto determine the needed duty cycle of the pulse width modulation (PWM)to control actuation of a valve (e.g., valve 52) to attain the desiredfluid-flow rate. Processor unit 82 may be configured to execute a seriesof instructions such that the flow-control device 50 and thefluid-movement device 60 are cooperatively controlled by the processorunit 82, e.g., based on determination of a desired fluid-flow rate usingtemperature data and/or flow data, to selectively adjust the fluid-flowrate in a fluid-flow path (e.g., first coolant path 19) of the coolantsupply system 11.

Feedback control system 14 may be adapted to control the flow-controldevice 50 to allow flow (e.g., valve 52 held open) for longer periods oftime as the sensed temperature rises, and shorter periods of time as thesensed temperature falls. Electrosurgical system 10 may be adapted tooverride PWM control of the flow-control device 50 to hold the valve 52open upon initial activation of the antenna assembly 112. For thispurpose, a timer may be utilized to prevent the control device 50 fromoperating for a predetermined time interval (e.g., about one minute)after the antenna assembly 112 has been activated. In some embodiments,the predetermined time interval to override PWM control of theflow-control device 50 may be varied depending on setting, e.g., timeand power settings, provided by the user. In some embodiments, theelectrosurgical power generating source 28 may be adapted to perform aself-check routine that includes determination that the flow-controldevice 50 is open before enabling energy delivery between theelectrosurgical power generating source 28 and the probe 100.

FIG. 3 is a block diagram of an electrosurgical system 300 including anembodiment of the electrosurgical power generating source 28 of FIG. 1that includes a generator module 86 in operable communication with aprocessor unit 82, a user interface 121 communicatively-coupled to theprocessor unit 82, and an actuator 122 communicatively-coupled to theuser interface 121. Actuator 122 may be any suitable actuator, e.g., afootswitch, a handswitch, an orally-activated switch (e.g., abite-activated switch and/or a breath-actuated switch), and the like.Probe 100 is operably-coupled, e.g., via transmission line 16 shown inFIG. 1, to an energy output of the generator module 86. User interface121 may include an indicator unit 129 adapted to provide a perceptiblesensory alert, which may be an audio, visual, such as an illuminatedindicator (e.g., a single- or variably-colored LED indicator), or othersensory alarm.

In some embodiments, the generator module 86 is configured to provideenergy of about 915 MHz. Generator module 86 may additionally, oralternatively, be configured to provide energy of about 2450 MHz (2.45GHz) or about 5800 MHz (5.8 GHz). The present disclosure contemplatesembodiments wherein the generator module 86 is configured to generate afrequency other than about 915 MHz or about 2450 MHz or about 5800 MHz,and embodiments wherein the generator module 86 is configured togenerate variable frequency energy.

Processor unit 82 according to various embodiments is programmed toenable a user, via the user interface 121, to preview operationalcharacteristics of an energy-delivery device, such as, for example,probe 100. Processor unit 82 may include any type of computing device,computational circuit, or any type of processor or processing circuitcapable of executing a series of instructions that are stored in amemory, e.g., storage device 88 or external device 81.

In some embodiments, a storage device 88 is operably-coupled to theprocessor 82, and may include random-access memory (RAM), read-onlymemory (ROM), and/or non-volatile memory (e.g., NV-RAM, Flash, anddisc-based storage). Storage device 88 may include a set of programinstructions executable on the processor unit 82 for controlling theflow-control device 50 based on determination of a desired fluid-flowrate in accordance with the present disclosure. Electrosurgical powergenerating source 28 may include a data interface 80 that is configuredto provide a communications link to an external device 81. In someembodiments, the data interface 80 may be any of a USB interface, amemory card slot (e.g., SD slot), and/or a network interface (e.g.,100BaseT Ethernet interface or an 802.11 “Wi-Fi” interface). Externaldevice 81 may be any of a USB device (e.g., a memory stick), a memorycard (e.g., an SD card), and/or a network-connected device (e.g.,computer or server).

Electrosurgical power generating source 28 may include a database 84that is configured to store and retrieve energy applicator data, e.g.,parameters associated with one or energy applicators, and/or other data(e.g., one or more lookup tables “T_(X,Y)”). Database 84 may also bemaintained at least in part by data provided by an external device 81via the data interface 80, e.g., energy applicator data may be uploadedfrom the external device 81 to the database 84 via the data interface80.

FIG. 4 shows an electrosurgical system 410 according to an embodiment ofthe present disclosure that includes the electrosurgical powergenerating source 28 and the probe 100 of FIG. 1 and a feedback controlsystem 414 operably associated with a coolant supply system 411 adaptedto provide coolant fluid “F” to the probe 100. In some embodiments, thefeedback control system 414 is adapted to provide athermal-feedback-controlled rate of fluid flow to the probe 100.

Coolant supply system 411 includes a substantially closed loop having afirst coolant path 419 leading to the probe 100, a second coolant path420 leading from the probe 100, and a diversion flow path 421 disposedin fluid communication with the first coolant path 419 and the secondcoolant path 420. Coolant supply system 411 generally includes thecoolant source 90, fluid-movement device 60, first coolant supply line66 leading from the coolant source 90 to the fluid-movement device 60,and the first coolant return line 95 leading to the coolant source 90 ofthe coolant supply system 11 of FIG. 1.

In contrast to the coolant supply system 11 of FIG. 1 that includes aflow-control device 50 disposed in fluid communication with the firstcoolant path 19 (fluidly-coupled to the inlet fluid port 179) and apressure-relief device 40 disposed in fluid communication with thediversion flow path 21, the coolant supply system 411 shown in FIG. 4includes a flow-control device 450 disposed in fluid communication withthe diversion flow path 421 (fluidly-coupled to the coolant source 90).In the embodiment shown in FIG. 4, the coolant path 419 includes asecond coolant supply line 467 leading from the fluid-movement device 60to the inlet fluid port 179 defined in the connection hub 142, and thediversion flow path 421 includes a second coolant return line 494fluidly-coupled to the second coolant supply line 467 and the firstcoolant return line 95, wherein the flow-control device 450 is disposedin fluid communication with the second coolant return line 494.

Feedback control system 414 includes a processor unit, e.g., processorunit 82 associated with the electrosurgical power generating source 28,or a standalone processor (not shown), operably associated with theflow-control device 450. Flow-control device 450 may include anysuitable device capable of regulating or controlling the rate of fluidflow passing though the flow-control device 450. In the embodiment shownin FIG. 4, the flow-control device 450 includes a valve 452 including avalve body 454 and an electromechanical actuator 456 operatively coupledto the valve body 454. In some embodiments, the actuator 456 is operablyassociated with the processor unit 82, e.g., via a transmission line 432or via wireless connection.

Processor unit 82 may be configured to control the flow-control device450 by activating the actuator 456 to selectively adjust the fluid-flowrate in the diversion flow path 421 to effect a desired change in thefluid-flow rate in the first coolant path 419 leading to the probe 100.In some embodiments, the processor unit 82 may be configured to controlthe flow-control device 450 by activating the actuator 456 toselectively adjust the fluid-flow rate in the diversion flow path 421based on determination of a desired fluid-flow rate using data receivedfrom one or more temperature sensors (e.g., two sensors “TS₁” and “TS₂”)and/or data received from one or more flow sensors (e.g., one sensor“FS₁”).

In some embodiments, the electrosurgical system 410 includes one or morepressure sensors (e.g., pressure transducer 70) disposed in fluidcommunication with one or more fluid-flow paths (e.g., first coolantpath 419) of the coolant supply system 411. In the embodiment shown inFIG. 4, the pressure transducer 70 is disposed in fluid communicationwith the first coolant path 419 located between the fluid-movementdevice 60 and the flow-control device 450.

FIG. 5 schematically illustrates a feedback control system 514 accordingto an embodiment of the present disclosure that includes the processorunit 82. Feedback control system 514 is similar to the feedback controlsystem 14 of FIG. 2, except for the addition of pressure sensors “PS₁”,“PS₂” through “PS_(K)”, where K is an integer, and description ofelements in common with the feedback control system 14 of FIG. 2 isomitted in the interests of brevity.

Processor unit 82 may be configured to enable the electrosurgical powergenerating source 28 for activating the probe 100 based on determinationthat the pressure level of fluid in one or more fluid-flow paths of thecoolant supply system 11 is above a predetermined threshold usingpressure data received from one or more pressure sensors “PS₁”, “PS₂”through “PS_(K)”. The pressure data may be transmitted via transmissionlines “L₈”, “L₉” through “L_(K)” or wirelessly transmitted. Processorunit 82 may additionally, or alternatively, be configured to stop energydelivery from the electrosurgical power generating source 28 to theprobe 100 based on determination that the pressure level in one or morefluid-flow paths of the coolant supply system 11 is above apredetermined threshold using pressure data received from one or morepressure sensors “PS₁”, “PS₂” through “PS_(K)”. Processor unit 82 mayadditionally, or alternatively, be configured to execute a series ofinstructions to control one or more operational parameters of anelectrosurgical power generating source 28 based on determination ofwhether the pressure level of fluid in the probe 100 and/or conduitfluidly-coupled to the probe 100 is above a predetermined thresholdusing pressure data received from one or more pressure sensors “PS₁”,“PS₂” through “PS_(K)”.

Hereinafter, methods of directing energy to tissue using a fluid-cooledantenna assembly in accordance with the present disclosure are describedwith reference to FIGS. 6 and 7. It is to be understood that the stepsof the methods provided herein may be performed in combination and in adifferent order than presented herein without departing from the scopeof the disclosure. Embodiments of the presently-disclosed methods ofdirecting energy to tissue may be implemented as a computer process, acomputing system or as an article of manufacture such as a pre-recordeddisk or other similar computer program product or computer-readablemedia. The computer program product may be a non-transitory,computer-readable storage media, readable by a computer system andencoding a computer program of instructions for executing a computerprocess.

FIG. 6 is a flowchart illustrating a method of directing energy totissue using a fluid-cooled antenna assembly according to an embodimentof the present disclosure. In step 610, an energy applicator 100 isprovided. The energy applicator 100 includes an antenna assembly 112 anda hub 142 providing one or more coolant connections (e.g., inlet fluidport 179 shown in FIG. 1) to the energy applicator 100.

In step 620, a coolant supply system 11 (or coolant supply system 411shown in FIG. 4) is provided. The coolant supply 11 includes afluid-flow path 19 fluidly-coupled to the hub 142 for providing fluidflow to the energy applicator 100. In some embodiments, the firstcoolant path 19 includes a first coolant supply line 66 leading from acoolant source 90 to a fluid-movement device 60, a second coolant supplyline 67 leading from the fluid-movement device 60 to a flow-controldevice 50, and a third coolant supply line 68 leading from theflow-control device 50 to the inlet fluid port 179.

Coolant source 90 may be any suitable housing containing a reservoir ofcoolant fluid “F”. Coolant fluid “F” may be any suitable fluid that canbe used for cooling or buffering the energy applicator 100, e.g.,deionized water, or other suitable cooling medium. Coolant fluid “F” mayhave dielectric properties and may provide dielectric impedancebuffering for the antenna assembly 112.

In step 630, the energy applicator 100 is positioned in tissue for thedelivery of energy to tissue when the antenna assembly 112 is energized.The energy applicator 100 may be inserted directly into tissue, insertedthrough a lumen, e.g., a vein, needle, endoscope or catheter, placedinto the body during surgery by a clinician, or positioned in the bodyby other suitable methods. The energy applicator 100 may be configuredto operate with a directional radiation pattern.

Electrosurgical energy may be transmitted from an energy source 28through the antenna assembly 112 to tissue. The energy source 28 may beany suitable electrosurgical generator for generating an output signal.In some embodiments, the energy source 28 is a microwave energy source,and may be configured to provide microwave energy at an operationalfrequency from about 300 MHz to about 10 GHz. In some embodiments, theenergy source 28 supplies power having a selected phase, amplitude andfrequency.

In step 640, a thermal-feedback-controlled rate of fluid flow isprovided to the antenna assembly 112 when energized, using a feedbackcontrol system 14 operably-coupled to a flow-control device 50 disposedin the fluid-flow path 19 leading to the energy applicator 100.

FIG. 7 is a flowchart illustrating a method of directing energy totissue using a fluid-cooled antenna assembly according to an embodimentof the present disclosure. In step 710, an energy applicator 100 isprovided. The energy applicator 100 includes an antenna assembly 112 anda coolant chamber 137 adapted to circulate coolant fluid “F” around atleast a portion of the antenna assembly 112.

In step 720, a coolant supply system that is adapted to provide coolantfluid “F” to the energy applicator 100 is provided. The energyapplicator 100 may be used in conjunction with coolant supply systems invarious configurations. The coolant chamber 137 of the energy applicator100 may be fluidly-coupled to a coolant supply system 11 according to anembodiment shown in FIG. 1 that includes a flow-control device 50disposed in fluid communication with a first coolant path 19 (e.g.,fluidly-coupled to the energy applicator 100 to provide fluid flow froma coolant source 90 to the energy applicator 100).

Alternatively, the coolant chamber 137 may be fluidly-coupled to acoolant supply system 411 according to an embodiment shown in FIG. 4that includes a flow-control device 450 disposed in fluid communicationwith a third coolant path 421 disposed in fluid communication with afirst coolant path 419 (e.g., fluidly-coupled to the energy applicator100 to provide fluid flow from a coolant source 90 to the energyapplicator 100) and a second coolant path 420 (e.g., fluidly-coupled tothe energy applicator 100 to provide fluid flow from the energyapplicator 100 to the coolant source 90).

In step 730, the energy applicator 100 is positioned in tissue for thedelivery of energy to tissue when the antenna assembly 112 is energized.The energy applicator 100 may be inserted into or placed adjacent totissue to be treated.

In step 740, a feedback control system 14 (or 414) including a processorunit 82 communicatively-coupled to one or more temperature sensors,e.g., one temperature sensor “TS₁”, associated with the energyapplicator 100 is used to provide a thermal-feedback-controlled rate offluid flow to the antenna assembly 112 when energized. Processor unit 82may be configured to control a flow-control device 50 (or 450)associated with the coolant supply system 11 (or 411) based ondetermination of a desired fluid-flow rate using one or more electricalsignals outputted from the one or more temperature sensors “TS₁”.Feedback control system 14 (or 414) may utilize data “D” (e.g., datarepresentative of a mapping of temperature data to settings for properlyadjusting one or more operational parameters of the flow-control device50 (or 450) to achieve a desired temperature and/or desired ablation)stored in a look-up table “T_(X,Y)”, or other data structure, todetermine the desired fluid-flow rate.

In some embodiments, the processor unit 82 is communicatively-coupled toone or more pressure sensors 70 disposed in fluid communication with oneor more fluid-flow paths (e.g., first coolant path 19) of the coolantsupply system 11 (or 411). Processor unit 82 may be configured to enablean electrosurgical generator 28 for activating the energy applicator 100based on determination that a sensed pressure level in the one or morefluid-flow paths is above a predetermined threshold using at least oneelectrical signal outputted from the one or more pressure sensors 70.

Processor unit 82 may additionally, or alternatively, be configured tocontrol one or more operating parameters associated with theelectrosurgical generator 28 based on determination that a sensedpressure level in the one or more fluid-flow paths (e.g., first coolantpath 19) is below a predetermined threshold using at least oneelectrical signal outputted from the one or more pressure sensors 70.Examples of operating parameters associated with the electrosurgicalpower generating source 28 include without limitation temperature,impedance, power, current, voltage, mode of operation, and duration ofapplication of electromagnetic energy.

In some embodiments, the coolant supply system 11 includes afluid-movement device 60 disposed in fluid communication with the firstcoolant path 19, and may include a second coolant path 20 (e.g.,fluidly-coupled to the energy applicator 100 to allow fluid flow toreturn to the coolant source 90) and a third coolant path 21 disposed influid communication with the first coolant path 19 and the secondcoolant path 20. A pressure-relief device 40 may be disposed in fluidcommunication with the third coolant path 21 and may allow thefluid-movement device 60 to run at a substantially constant speed and/orunder a near-constant load (head pressure) regardless of the selectiveadjustment of the fluid-flow rate in the first coolant path 19

The above-described systems for thermal-feedback-controlled rate offluid flow to electrosurgical devices and methods of directing energy totissue using a fluid-cooled antenna assembly may be used in conjunctionwith a variety of electrosurgical devices adapted for treating tissue.Embodiments may be used in conjunction with electrosurgical devicesadapted to direct energy to tissue, such as ablation probes, e.g.,placed percutaneously or surgically, and/or ablation devices suitablefor use in surface ablation applications.

The above-described systems including a feedback control system adaptedto provide a thermal-feedback-controlled rate of fluid flow to an energyapplicator disposed in fluid communication with a coolant supply systemmay be suitable for a variety of uses and applications, includingmedical procedures, e.g., tissue ablation, resection, cautery, vascularthrombosis, treatment of cardiac arrhythmias and dysrhythmias,electrosurgery, etc.

Although embodiments have been described in detail with reference to theaccompanying drawings for the purpose of illustration and description,it is to be understood that the inventive processes and apparatus arenot to be construed as limited thereby. It will be apparent to those ofordinary skill in the art that various modifications to the foregoingembodiments may be made without departing from the scope of thedisclosure.

What is claimed is:
 1. A method of directing energy to tissue by using afluid-cooled antenna assembly of an energy applicator, the methodcomprising: connecting the energy applicator to a hub, the hub coupledto a coolant supply system for providing fluid to the antenna assemblyof the energy applicator, the coolant supply system having a coolantsource, a first coolant supply line, a second coolant supply line, and athird coolant supply line in fluid communication with the coolantsource, the first coolant supply line connected between the coolantsource and a fluid-movement device, the second coolant supply linedirectly connected between a pressure transducer and the fluid-movementdevice, and the third coolant supply line directly connected between aflow-control device and the antenna assembly; positioning the energyapplicator in tissue; activating the energy applicator via anelectrosurgical generator; measuring a temperature of the fluid in theantenna assembly; controlling a thermal-feedback-controlled rate offluid flow based on the measured temperature of the fluid in the antennaassembly; providing fluid to the antenna assembly at thethermal-feedback-controlled rate of fluid flow using a feedback controlsystem including the flow-control device, the flow control deviceincluding a valve and an electro-mechanical actuator, and the feedbackcontrol system including a processor unit; and connecting the pressuretransducer to the valve, the pressure transducer disposed within thecoolant supply system; wherein the pressure transducer outputs a signalat a pressure below a burst pressure of a pressure relief valve toindicate to the electrosurgical generator that the fluid-cooled antennaassembly has coolant flowing therethrough and wherein the processor unittriggers a shut-off of the electrosurgical generator based on pressurelevels of the coolant in the fluid-cooled antenna assembly; and whereinthe processor unit outputs a signal indicative of an error code if apredetermined time elapses between energy delivery to the fluid-cooledantenna assembly and detection of the signal outputted by the pressuretransducer.
 2. The method of directing energy to tissue by using thefluid-cooled antenna assembly of claim 1, wherein the providing stepfurther includes controlling the flow-control device by activating theelectro-mechanical actuator to selectively adjust the rate of fluid-flowin response to at least one electrical signal received from at least onetemperature sensor which performs the measuring of the temperature ofthe fluid in the antenna assembly.
 3. The method of directing energy totissue by using the fluid-cooled antenna assembly of claim 2, whereinthe at least one temperature sensor is disposed within a distalradiating portion of the antenna assembly.
 4. The method of directingenergy to tissue by using the fluid-cooled antenna assembly of claim 2,wherein the at least one temperature sensor is disposed within a fluidreturn port defined in the hub.
 5. The method of directing energy totissue by using the fluid-cooled antenna assembly of claim 2, whereinthe processor unit is incorporated within the electrosurgical generatorand communicatively-coupled to the electro-mechanical actuator of theflow-control device.
 6. The method of directing energy to tissue byusing the fluid-cooled antenna assembly of claim 5, wherein theprocessor unit is further communicatively-coupled to at least one flowsensor.
 7. The method of directing energy to tissue by using thefluid-cooled antenna assembly of claim 1, wherein the electro-mechanicalactuator is controlled by pulse width modulation (PWM) techniques.
 8. Amethod of directing energy to tissue by using a fluid-cooled antennaassembly of an energy applicator, the method comprising: connecting theenergy applicator to a coolant supply system adapted to circulatecoolant fluid around at least a portion of the antenna assembly, thecoolant supply system having a coolant source, a first coolant supplyline, a second coolant supply line, and a third coolant supply line influid communication with the coolant source, the first coolant supplyline connected between the coolant source and a fluid-movement device,the second coolant supply line directly connected between a pressuretransducer and the fluid-movement device, and the third coolant supplyline directly connected between a flow-control device and the antennaassembly; positioning the energy applicator in tissue; activating theenergy applicator via an electrosurgical generator; measuring atemperature of the coolant fluid in the antenna assembly; controlling athermal-feedback-controlled rate of fluid flow based on the measuredtemperature of the coolant fluid in the antenna assembly; providingcoolant fluid to the antenna assembly at the thermal-feedback-controlledrate of fluid flow using a feedback control system including a processorunit configured to control the flow-control device, the flow controldevice having a valve and an electro-mechanical actuator by activatingthe electro-mechanical actuator to selectively adjust the rate offluid-flow in response to at least one electrical signal received fromat least one temperature sensor associated with the energy applicator;and connecting a pressure transducer with to the valve, the pressuretransducer disposed within the coolant supply system; wherein thepressure transducer outputs a signal at a pressure below a burstpressure of a pressure relief valve to indicate to the electrosurgicalgenerator that the fluid-cooled antenna assembly has coolant flowingtherethrough and wherein the processor unit triggers a shut-off of theelectrosurgical generator based on pressure levels of the coolant in thefluid-cooled antenna assembly; and wherein the processor unit outputs asignal indicative of an error code if a predetermined time elapsesbetween energy delivery to the fluid-cooled antenna assembly anddetection of the signal outputted by the pressure transducer.
 9. Themethod of directing energy to tissue by using the fluid-cooled antennaassembly of claim 8, wherein the electro-mechanical actuator iscontrolled by pulse width modulation (PWM) techniques.
 10. The method ofdirecting energy to tissue by using the fluid-cooled antenna assembly ofclaim 8, wherein the pressure transducer allows the fluid-movementdevice to operate under a near-constant load.
 11. The method ofdirecting energy to tissue by using the fluid-cooled antenna assembly ofclaim 8, wherein the coolant supply system includes a closed loopconfiguration such that coolant fluid does not contact tissue, theclosed loop configuration having a first coolant path leading to theantenna assembly from the coolant source and a second coolant pathleading from the antenna assembly to the coolant source, the firstcoolant path formed by the first, second, and third coolant supplylines.
 12. The method of directing energy to tissue by using thefluid-cooled antenna assembly of claim 8, wherein the processor unit isfurther configured to control at least one operating parameterassociated with the electrosurgical generator.
 13. The method ofdirecting energy to tissue by using the fluid-cooled antenna assembly ofclaim 12, wherein the at least one operating parameter associated withthe electrosurgical generator is selected from the group consisting oftemperature, impedance, power, current, voltage, mode of operation, andduration of application of electromagnetic energy.